Advanced Program Control 33113
The argument commandcan be either a string constant or a pointer to a string. For exam-
ple, to obtain a directory listing in DOS, you could write either
system(“dir”);
or
char *command = “dir”;
system(command);
After the operating system command is executed, execution returns to the program at the
location immediately following the call to system(). If the command you pass to sys-
tem()isn’t a valid operating system command, you get a Bad command or file name
error message before returning to the program. The use of system()is illustrated in
Listing 13.9.LISTING13.9 system.c. Using the system()function to execute system commands
1: /* Demonstrates the system() function. */
2: #include <stdio.h>
3: #include <stdlib.h>
4:
5: int main( void )
6: {
7: /* Declare a buffer to hold input. */
8:
9: char input[40];
10:
11: while (1)
12: {
13: /* Get the user’s command. */
14:
15: puts(“\nInput the desired system command, blank to exit”);
16: gets(input);
17:
18: /* Exit if a blank line was entered. */
19:
20: if (input[0] == ‘\0’)
21: exit(0);
22:
23: /* Execute the command. */
24:
25: system(input);
26: }
27: return 0;
28: }21 448201x-CH13 8/13/02 11:12 AM Page 331